SUNRPC: Prevent kernel stack corruption on long values of flush
The buffer size in read_flush() is too small for the longest possible values
for it. This can lead to a kernel stack corruption:
[ 43.047329] Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: ffffffff833e64b4
[ 43.047329]
[ 43.049030] Pid: 6015, comm: trinity-child18 Tainted: G W 3.5.0-rc7-next-20120716-sasha #221
[ 43.050038] Call Trace:
[ 43.050435] [<ffffffff836c60c2>] panic+0xcd/0x1f4
[ 43.050931] [<ffffffff833e64b4>] ? read_flush.isra.7+0xe4/0x100
[ 43.051602] [<ffffffff810e94e6>] __stack_chk_fail+0x16/0x20
[ 43.052206] [<ffffffff833e64b4>] read_flush.isra.7+0xe4/0x100
[ 43.052951] [<ffffffff833e6500>] ? read_flush_pipefs+0x30/0x30
[ 43.053594] [<ffffffff833e652c>] read_flush_procfs+0x2c/0x30
[ 43.053596] [<ffffffff812b9a8c>] proc_reg_read+0x9c/0xd0
[ 43.053596] [<ffffffff812b99f0>] ? proc_reg_write+0xd0/0xd0
[ 43.053596] [<ffffffff81250d5b>] do_loop_readv_writev+0x4b/0x90
[ 43.053596] [<ffffffff81250fd6>] do_readv_writev+0xf6/0x1d0
[ 43.053596] [<ffffffff812510ee>] vfs_readv+0x3e/0x60
[ 43.053596] [<ffffffff812511b8>] sys_readv+0x48/0xb0
[ 43.053596] [<ffffffff8378167d>] system_call_fastpath+0x1a/0x1f
Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
Cc: stable@kernel.org
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 2a68bb3..fc2f7aa 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -1409,11 +1409,11 @@
size_t count, loff_t *ppos,
struct cache_detail *cd)
{
- char tbuf[20];
+ char tbuf[22];
unsigned long p = *ppos;
size_t len;
- sprintf(tbuf, "%lu\n", convert_to_wallclock(cd->flush_time));
+ snprintf(tbuf, sizeof(tbuf), "%lu\n", convert_to_wallclock(cd->flush_time));
len = strlen(tbuf);
if (p >= len)
return 0;